Diana Bertuol Garcia

Topic

Restoration success in times of change: using trait-based approaches to investigate restoration predictability and community outcomes in grasslands

School of Environmental Studies

Date & location

• Monday, August 31, 2026

• 12:00 P.M.

• Virtual Defence

Reviewers

Supervisory Committee

• Dr. Nancy Shackelford, School of Environmental Studies, University of Victoria (Supervisor)

• Dr. Gustavo Paterno, School of Environmental Studies, UVic (Member)

• Dr. Daniel Laughlin, Department of Botany, University of Wyoming (Outside Member)

• Dr. Emma Ladouceur, Department of Biology, University of Prince Edward Island (Outside Member) 

External Examiner

• Dr. Viktoria Wagner, Department of Biological Sciences, University of Alberta 

Chair of Oral Examination

• Dr. Donald Juzwishin, School of Health Information Science, UVic

   

Abstract

Ecosystems worldwide are experiencing unprecedented degradation due to anthropogenic impacts, driving growing societal and policy interest in ecological restoration. However, restoration is challenged by unpredictable outcomes and changing climatic conditions. Functional ecology offers promise for improving restoration under global change, but trait-based approaches remain limited by knowledge gaps and implementation challenges. Therefore, further studies on the factors affecting restoration predictability, as well as the ecological processes and functional traits governing responses to climate change, are fundamental to increase restoration success. This dissertation uses a trait-based perspective to examine different dimensions of restoration success in a changing world, with a focus on grassland ecosystems. In chapter 1, I examine how land-use history and management actions predict grassland restoration outcomes, and how predictability changes with aridity. Using data from 11 restoration projects, I show that restoration outcomes linked to dominant species are more predictable than those related to rare species. Moreover, I show that aridity impacts predictability of certain outcomes. These results clarify when, where, and with what outcomes restoration practitioners might be better able to achieve grassland restoration targets. In chapter 2, I then focus on the ecological mechanisms driving grassland response to extreme drought, which are expected to increase under climate change. I use data from a globally distributed drought experiment to disentangle the relative importance and joint influence of plant functional composition, diversity, and climate on the resistance of aboveground net primary productivity. In contrast to widespread emphasis in the literature on biotic drivers of resistance, the long-term aridity of the site emerged as a key determinant of drought resistant. This highlights the importance of considering the restoration site’s climatic context alongside management strategies targeting diversity or traits. Chapter 3 then transposes the same question to a local context using a common garden experiment. However, theoretical expectations were contrasted against real-world challenges, including simulating drought, achieving trait targets, and addressing dominance of exotic species in old agricultural fields. I use these unexpected results as opportunities to draw lessons for ecological experiments and successful trait-based grassland restoration. I highlight the challenges of achieving trait targets under severe agricultural legacy, and argue for better integration of complexities of restoration with ecological science. Finally, chapter 4 addresses real-world restoration constraints related to the commercial availability of native plants within the regional restoration market. Using oak-prairie ecosystems in the Pacific Northwest as a study system, I compare the species and diversity of the regional flora with the species commercially available from plant suppliers. I show that the commercial species pool is a less diverse, biased subset of the flora, limiting the ability of restoration efforts to establish diverse, functionally representative communities capable of withstanding environmental change. Overall, this dissertation demonstrates that restoration outcomes cannot be understood in isolation from their environmental context. Grassland restoration success is shaped by interactions among climatic conditions, community processes, and real-world constraints, including those arising from historical legacies and restoration markets. Moreover, while trait-based approaches offer valuable insights into the mechanisms underlying community responses to environmental change, their broader application in restoration is still challenged by data availability and context-dependence.